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In one sense, all FLUTe applications are unique in that these methods did not exist before 1989. However, some methods have become so commonly used that they are no longer unfamiliar. Those common methods are:
1. Blank liners for sealing boreholes.
2. Transmissivity profiles of open boreholes for rapid high resolution measurements.
3. Water FLUTe installations for multi-level water samples and head measurements.
4. NAPL FLUTe installations to map LNAPL and DNAPL of many kinds.
There have been extensions of these methods to smaller diameter holes, more artesian holes, and deeper holes. However, these are variations on the FLUTe systems commonly used.
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The following descriptions are of applications of FLUTe methods not so widely used and perhaps not known to many FLUTe users. Some are applications that should be used more frequently because of the advantages.
Unique Applications
Installations with Artesian Conditions
In the early days of FLUTe methods, if the water table was very shallow or the well somewhat artesian, a heavy mud was used instead of water to pressurize the liner after it had been installed. The installation was usually done off of a scaffold to obtain a sufficient excess driving head to evert the liner. However, FLUTe has developed several designs, with patents pending, which allowed the installation of everting liners into boreholes with 20 ft of artesian head and flow rates out the top of the casing of 100-150 gal/min. Very good transmissivity profiles have been obtained in such holes. Such extreme artesian conditions often lead to a final liner fill of a bentonite/cement grout for a long term Water FLUTe installation. The liner is not then removable as are other FLUTe installations.
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Installations in Karst Terrain
Installations in karst boreholes of many kinds for many purposes are drilled into karst formations. The boreholes are difficult to seal and therefore isolating sampling intervals, grouting of casing, and other common functions are more difficult to nearly impossible in karst. The continuous lining capability of FLUTe systems without the use of grout makes those difficulties much less of a concern.
Sealing casing strings in karst formations
Grouting the annulus can be very expensive in karstic limestone because large quantities of expensive grout are sometimes lost to the karst solution channels. Loss of returns while drilling is further evidence of the problem. The grout seal can be compromised by the loss of grout into the formation and subsequent leakage from the lower production zone to upper aquifers. The mixing of mud, which is used to support the borehole wall with the grout injected to seal the annular space between the casing and formation, can lead to a weak and permeable seal in the annulus. The annular grout can mix with formation fluids to degrade its in-situ chemistry and strength. A high pressure gradient on a grout column during curing may also lead to a porous and permeable grout. This difficulty can be encountered in water wells, oil wells, or “fracking” wells. A high strength, flexible FLUTe liner can be installed prior to or during the insertion of the casing, eliminating the above difficulties. The annulus can be grouted through a trimmie pipe in stages in order to not burst the liner with a high pressure grout column and without any loss of grout to the formation or mixing with the borehole fluids. This is done routinely in the installation of FLUTe liners in ground water investigations. The formation fluids and drilling muds are forced out of the borehole by the everting liner prior to the grout injection between the liner and the casing or the mud can also be pumped from beneath the liner during the liner installation. The neighboring drawing is a visual representation of the procedure.
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Well Development
It has been observed that the removal of a flexible liner draws down the head beneath the liner by as much as 100 feet, especially near the bottom of the hole. That low pressure beneath the liner as it is being removed tends to extract mud and cuttings from fractures that may not otherwise be cleared in the normal well development procedures. This process and an explanation of why boreholes may not otherwise be well developed is described in the conference presentation titled: “Open Hole Well Development Problems and Solutions” in the publications section.
Injection of Remediation Fluids
Some FLUTe liners have been fitted with tubing much like that of a Water FLUTe but without any check valves and usually with larger diameter tubing than that used in the Water FLUTe sampling system. The tubing is then used to inject remediation fluids into discrete intervals. In some cases, some of the intervals are used for monitoring the arrival of remediation fluids. Special liners of more resistant fabrics than the standard nylon liner have been used to avoid damage by the fluids injected. For information on those designs, contact us.
Liner augmentation of horizontal drilling (LAHD)
Flexible liners were first tested in augmentation of horizontal drilling in Mustang, OK in 1997.
The method is described in the publication LAHD presentation 2002 which describes the first
commercial application of the method to emplace sampling intervals under a landfill in Indianapolis,
IN. The basic advantage of the technique is that it replaced the mud cake of a horizontal drill hole
with a flexible liner which liner can also carry a variety of instruments into position beneath buildings, highways, and landfills. The method has not been extensively used primarily because FLUTe has not advertised the option.
Landfill monitoring in a prefabricated layered subsurface
Many current landfill monitoring designs either monitor the landfill within the containment system (e.g., a leachate collection layer between the first and second liner) or outside the containment system in the ground water. For landfills located above deep vadose zones, a major leak will not be detected until a large portion of the vadose zone is contaminated if the monitoring system is ground water wells. FLUTe has designed a landfill monitoring design which has a much higher probability of detection of a leak early in the leak history. The same system provides many other advantages such as measurement of the leak rate, sampling the leak for composition, and even the remedy of the leak as part of the monitoring design. That system monitors the entire plane beneath the landfill outside of the landfill liners and does not include instruments which can fail in time so as to lose their monitoring capability. The design is described in the papers provided in the publications section under landfill monitoring.
Monitoring beneath a landfill in vertical wells
In some situations, the monitoring beneath a landfill or building is preferred in vertical wells. The ability of a propagating liner to travel horizontally and through turns in the piping was used in one situation and is planned for another. The first situation was in a brown field with an existing set of wells. A very large building was to be constructed on the site and it was desired to continue a soil vapor extraction remediation and monitoring of the same wells beneath the building. It was not desirable to have the vertical wells protrude through the floor of the building. In order to obtain water samples and make head measurements beneath the building, horizontal piping was installed in trenches beneath the building which ran from a vault outside the building, through various turns, to sweep elbows connecting to the vertical wells. FLUTe single sampling port systems were installed in the horizontal piping for distances of several hundred feet. The piping was 3 and 4 inch diameter with sweep elbows in the turns.
In a more recent design, larger horizontal piping is to be installed beneath a landfill as it is being constructed to allow access to vertical wells beneath the landfill with multiple sampling intervals. Details of the horizontal path to vertical wells for monitoring are provided in the white paper “FLUTe Wells Under Landfills and Buildings”. FLUTe has numerical models which predict the driving pressure needed to overcome drag, gravity, and turn angles for tortuous passages of specified geometry and liner assemblies of various characteristics such as weight, length, friction coefficient and diameter of liner. The models have been well tested against actual installations (see "Installations in tortuous passages" in this section). These installations are easier than the installations in horizontal drill holes as the hole is being drilled in the liner augmentation of horizontal drilling used beneath existing landfills.
Landfill monitoring in vertical wells down gradient
Many current landfills have common water wells down gradient from the landfill for the purpose of monitoring leachate leakage from the landfill. Obviously, the more closely spaced the wells and the varied the depths of the wells, the greater the probability that the well system can intercept a leachate leak. However, the installation of many traditional screened wells is very expensive to construct and to sample. A more practical approach is to use multi-level sampling systems and to purge them sufficiently to develop a large draw down to capture even a long slender leachate plume. This requires multi-level sampling systems which can produce large purge volumes to draw ground water from a significant distance from the well. The Water FLUTe systems are well suited for that application in that the several sampling intervals can be purged simultaneously and produce a gallon or more per stroke of the system for each port. This allows realistic purge volumes as large as 55 gallons. Water FLUTes can be constructed with even larger production per stroke of each pumping system.
The ability to purge all the sampling intervals simultaneously is due to the unique FLUTe design which has each pumping system at the same depth independent of the elevation of the sampling intervals. The ability to obtain a large volume per stroke is because the entire hole volume inside the liner is available for relatively large diameter tubing. The sealing liner occupies an insignificant portion of the hole volume. See the Water FLUTe sampling procedure for a more detailed description of the system.
Mapping of subsurface flow
One technique for doing that uses a transparent borehole flexible liner to observe in time the arrival of dyes or remediation fluids such as potassium permanganate injected into the formation in a nearby borehole.
There are a number of interesting options for monitoring tracer arrivals with the Water FLUTe system which is well suited to monitor for both pressure changes or for tracer arrivals. The tracer arrivals are particularly easy since all the sampling systems can be short stroked simultaneously to “sip” on the medium with minimal perturbation of the natural flow state. The continuously sealed hole also makes the monitoring hole a minimum perturbation on the flow field.
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Leak detection
FLUTe has a patented method which employs an advancing and a retreating liner (one everting, the other inverting) with a constant sampling interval between them. This allows, for example, a vacuum to be applied to the interval to extract any gas or liquid flowing through the hole wall or pipe wall into the interval between the two liners. The method is called “a progressive packer”. The advantages are several in that the liner travel is very gentle while providing an excellent isolation of the traveling interval from the rest of the borehole or pipe.
Logging of boreholes
The description of geophysical applications treats the method of towing longing sondes through open passages while the passage is supported and sealed with a blank propagating liner. This is especially attractive for sondes such as neutron moisture measurements. However, many kinds of sondes can be towed into passages that are relatively unstable or flowing fluids with minimal risk of loss of the tool. In other situations, contaminants in the borehole, such as coal tar, are incompatible with many sondes and the liner protects the sonde from contact with those fluids. See the Geophysical applications PDF for sondes that can “see” through the liner.
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Other uses for lining of piping and boreholes
FLUTe has in the past installed cure-in-place liners, such as resin soaked carbon fiber liners, in tortuous passages from the basement 100 ft upward to the roof gutters of the Smithsonian Museum of Natural History. The purpose was to line and seal rotting cast iron piping. Those applications are not common for FLUTe, but do use the special art and science of flexible liners as developed by FLUTe and the unique ancillary equipment of FLUTe design.
A much more common need is for deep boreholes drilled through karstic formations (e.g., oil and gas wells) to prevent the loss of the grout seal between the casing and the borehole wall. In karst formations, the sealing grout flows freely into the solution channels and caverns and prevents a high quality seal of the annulus which allows potential vertical leakage of brines, petroleum or gas into overlying potable aquifers. FLUTe has a design whereby the borehole is lined as the casing is being installed to prevent the loss of the sealing grout into the formation. Contact us for details.
Installations in tortuous passages
The ability to install a flexible liner by eversion into tortuous passages is particularly useful for the landfill monitoring, geophysical applications, relining of piping and other applications. The fact that the liner also seals the passage is an additional advantage as well as the ability to support the hole wall as a pressurized liner. This combination of characteristics allows many other applications and the customer is invited to consider these characteristics as they may be applied in novel applications. A video is available of a test of the FLUTe calculation model of liner propagation around numerous turns. The test showed excellent agreement with FLUTe’s model which was used to judge the feasibility of installations such as in the pipes in the walls of the Smithsonian.
Installations in lakes and ponds and other uses
Liners do not need a borehole or pipe to guide the eversion process. A liner can be everted across a cafeteria floor with many chair and table leg obstacles. The everting liner tends to deflect past such obstacles. It is also interesting that an air filled liner can be everted across a lake. A chain attached inside the liner can keep it oriented with a designated top side. In the same manner, a water filled liner with appropriate weighting can propagate across the bottom of a pond. The liners can be fitted with many kinds of instruments for sample collection, temperature measurements, etc…, in these applications.It is also interesting that a pressurized liner can be everted unsupported through the air for significant distances. The Geophysical applications presentation shows examples of that kind of propagation for small (2” diam.) liners. With reasonable guy lines built into the liners, a tower formed by an everting liner can be erected in a few minutes to 50-100 ft. from a small pressure canister. Liners filled with special fluids can be propagated for long distances for interesting uses. FLUTe has proposed the use of everting liners to quickly lay water lines for fighting forest fire. Contact us to discuss any novel applications. We may have already done it.
Video: Pressurized liner eversion through a series of pipe bends
SPACER